This invention relates generally to the field of reconstructing and/or manipulating surface geometries of one or more three dimensional objects in a scene, from a plurality of two dimensional images of the scene, and more particularly to a system and method for relating a local coordinate system associated with a reconstruction of at least a portion of the scene to a global coordinate system.
Reconstruction and/or manipulation (generally, xe2x80x9creconstructionxe2x80x9d) of surface features of three-dimensional object(s) in a scene, from a plurality of two-dimensional images of the object(s), is useful in a number of applications. U.S. patent application Ser. No. 08/989,047, filed Dec. 11, 1997, in the names of Dan Albeck et al., and entitled xe2x80x9cApparatus And Method For 3-Dimensional Surface Geometry Reconstruction,xe2x80x9d now U.S. Pat. No. 5,617,151, issued Dec. 26, 2000, (hereinafter referred to as the xe2x80x9cAlbeck applicationxe2x80x9d) describes an apparatus for performing such reconstruction using a rig including an optical head of three cameras, using a tensor arrangement described in U.S. patent application Ser. No. 08/497,224, filed Jun. 30, 1995, in the name of Amnon Shashua, and entitled xe2x80x9cApparatus And Method For Recreating And Manipulating A 3D Object Based On A 2D Projection Thereofxe2x80x9d now U.S. Pat. No. 5,821,943, issued Oct. 13, 1998, (hereinafter referred to as the xe2x80x9cShashua applicationxe2x80x9d) to generate information regarding reconstruction for the features of the object(s) from three images generated by the cameras. In the arrangement described in the Shashua application, the surface features that are reconstructed are defined by points that have coordinates in a coordinate system relative to one of the cameras in the rig. A problem arises in reconstruction if the surface features that are to be reconstructed cannot all be recorded by all of the cameras with the rig in one position. The apparatus described in the Albeck application provides a mechanism for moving the rig so as to allow the cameras to record sets of images of various portions of the surface(s) of the object(s). However, when the rig moves from one location, in which the cameras record a set of images of one portion of the object(s), to another location, in which the cameras record another set of images of another portion of the object(s), the coordinate system for the points defining the surface features of the various portions of the object(s) also changes.
In order to utilize the reconstruction information generated in the two xe2x80x9clocalxe2x80x9d coordinate systems in a unitary manner in connection with the object(s) in the scene, it is necessary to relate the local coordinate systems to a common global coordinate system, which will allow all of the points of the various portions of the reconstructed object(s) to be related to the global coordinate system, effectively xe2x80x9cstitchingxe2x80x9d the reconstructions together. The global coordinate system can conveniently be one of the two local coordinate systems that were used in the reconstruction, or it can be a third coordinate system, but in any case all of the points for the various portions of the reconstructed object need to be related to the global coordinate system. When a rig, such as the rig described in the Albeck application is moved from one position to another, to facilitate recording of sets of images of different portions of the object(s), the movement comprises one or both of a translation and a rotation of the rig, both in three dimensions. If the translational and rotational movement of the rig can be controlled sufficiently precise, the relation of the coordinate system after movement to the coordinate system before movement can easily be determined. However, if, for example, the mass of the rig is sufficiently large, in a number of applications the movement of the rig cannot readily be controlled sufficiently precisely to allow sufficiently precise reconstruction.
U.S. patent application Ser. No. 09/165,687, filed Oct. 2, 1998, in the name of Tamir Shalom, et al., and entitled xe2x80x9cSystem And Method For xe2x80x9cStitchingxe2x80x9d A Plurality Of Reconstructions Of Three-Dimensional Surface Features Of Object(s) In A Scene Defined Relative To Respective Coordinate Systems To Relate Them To A Common Coordinate System,xe2x80x9d now U.S. Pat. No. 6,201,541, issued Mar. 13, 2001, (hereinafter referred to as the Shalom application) describes an arrangement for relating a reconstruction of a portion of a scene to a global coordinate system. In the arrangement described in the Shalom application, a reconstruction of one portion of a scene is generated, which is related to the global coordinate system. Reconstructions of other portions can be related to the global coordinate system, but in the arrangement described in the Shalom application, the respective pairs of reconstructed portions will need to overlap with each other. That is, reconstructions successively displaced from the reconstruction which was originally related to the global coordinate systems will need to overlap, at least to some extent, with the overlapping portions providing information that is used to relate the local coordinate systems of the overlapping portions, thereby facilitating relation of the sequence of local coordinate systems to each other and, ultimately, to the global coordinate system. However, it will be appreciated that errors can develop in relating local coordinate systems of successive pairs of reconstructions, which can result in successively increasing errors in relating the local coordinate systems of the respective reconstructions to the global coordinate system. In addition, when the optical head is moved from one location to another to facilitate recording images from which the respective reconstructions are generated, the movement needs to be rigid, that is, the cameras need to maintain their respective orientations with respect to each other. If the optical head is not rigid, that is, if the cameras change their translational or rotational orientations with respect to each other, errors in relating the local coordinate systems of the respective pairs of reconstructions can also develop.
The invention provides a new and improved system and method for aligning a locally-reconstructed three-dimensional object to a global coordinate system using partially-detected control points.
In brief summary, the invention provides a system and method for aligning a locally-reconstructed three-dimensional object, whose local reconstruction is relative to a local coordinate system, to a global coordinate system by using pre-mapped control points which are projected onto one or more of the images that may be used to generate the local reconstruction. A system in accordance with the invention includes a control point information generator and an alignment generator. The control point information generator is configured to identify in at least image associated with a local reconstruction of said object a projection of at least one control point in the scene onto said at least one image, and generate local projected coordinate information indicating coordinates of said projection in said at least one image. The alignment information generator is configured to utilize said local projected coordinate information and mapping information relating to global coordinate information indicating coordinates of said at least one control point relative to said global coordinate system to generate alignment information relating a local coordinate system associated with said local reconstruction to said global coordinate system.
After the alignment information has been generated, the reconstruction in the local coordinate system can be aligned to the global coordinate system. This can be done with a plurality of local reconstructions, essentially stitching them together.